Creating concurrent crossfades

Parameters like RGB are always LTP, so to have them 'continue' in the background simply don't record values in the subsequent cues.
(Or delete them afterwards)

Movefade and Lockfade apply to the Intensity (HTP) transition.

So you'll want to use a Movefade so the Intensity transition runs as desired, and make sure that cues for each half of the set only include channels from that half of the set.

You can do that by putting your Sequence onto a Master, then select the channels for each cue and use [Record] & [Master_Key] to record "only selected channels" into each Cue/Preset.

(Could also use [Record] & [Preset] for only selected, then manually add the Preset to the sequence afterwards)

O, light the two halves of the set separately when recording each cue (so one side is off and thus not recorded).

If it's usually the same set of channels for each 'half' of the set, then the easiest way would be to create a Channel Partition for each half of the set and change to the right partition when editing/recording recording for each half.

To correct your existing cues, simply delete all the channels in the 'other half' from each Cue/Preset.

Parameters like RGB are always LTP, so to have them 'continue' in the background simply don't record values in the subsequent cues.
(Or delete them afterwards)

Movefade and Lockfade apply to the Intensity (HTP) transition.

So you'll want to use a Movefade so the Intensity transition runs as desired, and make sure that cues for each half of the set only include channels from that half of the set.

You can do that by putting your Sequence onto a Master, then select the channels for each cue and use [Record] & [Master_Key] to record "only selected channels" into each Cue/Preset.

(Could also use [Record] & [Preset] for only selected, then manually add the Preset to the sequence afterwards)

O, light the two halves of the set separately when recording each cue (so one side is off and thus not recorded).

If it's usually the same set of channels for each 'half' of the set, then the easiest way would be to create a Channel Partition for each half of the set and change to the right partition when editing/recording recording for each half.

To correct your existing cues, simply delete all the channels in the 'other half' from each Cue/Preset.

Thanks.  This mostly works.  I think my original problem was that I am using MIDI control with explicit cue numbers, which is equivalent to GOTO - and that cancels the ongoing fades.  Changing to MSC GO allows the fade to continue.

I still have two problems.  The background fade locks control of some devices with attributes - even those not included in the preset (I have explicitly deleted unused devices and attributes from the preset).  I have used a workaround by starting a short movefade using the problem devices just before the long movefade so that they aren't included.

The other is that the background fade levels cannot be reduced by later presets and have to run to completion.  (Including crossfades, which I think ought to cancel background fades and crossfade from the current levels - the same as if the first fade hadn't been moved to the background).  I have used two workarounds to this: 1: make sure the background fade completes well before the overriding cue is needed and 2: use GOTO or MSC GO with cue number.